Seven patients with renal cell carcinoma, who had undergone uninephrectomy or who had only one functioning kidney were clinicopathologically studied. They were 5 males and 2 females, with ages ranging from 51 to 74 years (mean: 61 years). Of these cases, 4 had undergone uninephrectomy for renal cell carcinoma, and 1 had received uninephrectomy because of renal calculus. In the remaining 2 cases, one kidney did not function (hypoplastic kidney). Renal cell carcinoma was discovered by macroscopic hematuria in 2 cases, during the follow-up observation after a previous surgical treatment of renal cell carcinoma in 4 cases and by abdominal computed tomography during treatment of abdominal aneurysm in 1 case. Excluding one case with multiple metastases, all cases were surgically treated (3 with partial nephrectomy and 3 with enucleation). During surgery, renal blood vessels were clamped for 24-60 minutes (mean: 38 minutes). After operation, 5 cases showed an elevation in serum creatinine (greater than or equal to 2.0 mg/ml), which, however, was normalized rapidly by conservative treatment. They have been followed up for 6 months to 7 years and 8 months after operation (mean: 2 years and 11 months). The case which had undergone before and recently received enucleation (2 pieces) showed metastasis of cancer to the pancreas 2.5 years after the recent operation. Therefore, this case additionally received partial pancreatectomy. The results of this study suggest that conservative surgical treatments are appropriate for the treatment of renal cell carcinoma in patients with solitary kidney from viewpoint of the quality of life, so long as postoperative management is sufficiently made.